So London wakes up this weekend to Mayor Johnson, year zero of the Age of Boris. Should we all be delighted, as so many of our fellow-citizens clearly hope? Terrified, as some residents of G2 are, cowering in their attics, awaiting the knock at the door? Should we laugh at the prospect of enjoyable chaos, mitigated by the knowledge that Labour's blueprint for London mayor was a Lilliputian model in which the mayor is roped down?

Perhaps we should fantasise about running hot and cold peasant girls at every bus stop, free champage (Bullingdon label) on the tube and in all 4x4 SUVs, all Londoners entitled to appear on Have I Got News For You at least once? Or should we get serious, as Mayor Johnson will have to from here on? His success or failure between now and the next general election is too important to Brand Cameron to be left to chance, let alone to the new mayor.

So Boris will have well-vetted advisers and officials to buttress his erratic talents and keep him under tight control. His policy differences with Ken Livingstone were, mostly, fewer than voters might have expected. Both men borrowed each other's ideas. After months of debate what most Londoners know most clearly is that their new mayor wants to get rid of unpopular bendy buses and restore the much-loved Routemaster (junked by Livingstone). They also know he hasn't a clue how to do it - and probably won't.

What worries them? Crime and the fear of crime in their neighbourhoods. A shortage of affordable housing, rented or for buying, for young people and key workers in public services, teachers and nurses. He wants to build 50,000, re-deploy 80,000 empty ones. A cleaner environment (10,000 more trees and less graffiti) and better transport flows, public and private. Better opportunities for youngsters, to encourage them to stay off the streets, out of gangs and focused on education - far too many young Londoners lack the skills or marketability to get their share of the capital's prosperity. A stronger sense of fairness and opportunity - schools, jobs, healthcare - in a very rich city where there are too many poor people.

Most of these issues are outside the mayor's remit or only tangentially within it. First and foremost, he must speak for the capital in London and to the wider world. Livingstone was a very recognisable London type, loved and hated. Johnson is a more exotic creature - a "love him or hate him, Marmite politician" - but with considerable potential, as yesterday's turnout showed. It's about leadership. An elusive talent, as Gordon Brown has discovered.

In policy terms Boris Johnson has promised to reform the congestion charge (no £25 charge for Chelsea tractors) but to retain concessionary travel passes for old and young (though some advisers would like to curb this popular perk); he supports Ken Livingstone's low-emission zone and wants to protect the parks from some of the people who voted for him; he wants affordable "family-sized" homes. Whereas the outgoing mayor backed the push for community policing - in collaboration with the Met's Sir Ian Blair - Boris would deploy extra officers in different ways, on trains and buses for instance.

Some would be armed with mobile scanners to check more easily for hidden weapons in public. Buses would be equipped with CCTV cameras. "Political correctness" in the Met would be rooted out - whatever that means; it has hardly been a bastion of multiculturalism; far from it until recent progress at making it look more like the city it polices.

Mayor Boris wants a no-strike deal with the powerful RMT union, which he says "holds the tube to ransom", though badly managed investment and poor signalling are far more disruptive of daily journeys. As a biker he wants to encourage more cycling. He wants to fine utilities that fail to meet their timetable for digging up roads.

It is not hard to be sceptical about the feasibility of some such campaign talk or to wonder how Mayor Johnson can reconcile contradictory commitments - not least the expectations he has generated in the resentful suburbs that it is their turn to be the mayor's priority. Tories have played the suburban card for a century, against evidence that London works better when it has strong central direction. That is one reason why it was unhappy between Ken's abolition as Mr GLC in 1986 and his reinvention as elected mayor in 2000.

One problem raised by the New Local Government Network last month was that the 25-strong London assembly is too weak to control the mayor, its weapons of scrutiny and accountability not suited to effective day-to-day restraint. Mayor Johnson will have his honeymoon, but for the People's Boris this is his first really grown-up job. It is a risk for him, a risk for London. One way or another he is likely to surprise us all.